Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that it is proper to the rational nature to act for an end. For man, to whom it belongs to act for an end, never acts for an unknown end. On the other hand, there are many things that have no knowledge of an end; either because they are altogether without knowledge, as insensible creatures: or because they do not apprehend the idea of an end as such, as irrational animals. Therefore it seems proper to the rational nature to act for an end.

Objection 2: Further, to act for an end is to order one's action to an end. But this is the work of reason. Therefore it does not belong to things that lack reason.

Objection 3: Further, the good and the end is the object of the will. But "the will is in the reason" (De Anima iii, 9). Therefore to act for an end belongs to none but a rational nature.

On the contrary, The Philosopher proves (Phys. ii, 5) that "not only mind but also nature acts for an end."

I answer that, Every agent, of necessity, acts for an end. For if, in a number of causes ordained to one another, the first be removed, the others must, of necessity, be removed also. Now the first of all causes is the final cause. The reason of which is that matter does not receive form, save in so far as it is moved by an agent; for nothing reduces itself from potentiality to act. But an agent does not move except out of intention for an end. For if the agent were not determinate to some particular effect, it would not do one thing rather than another: consequently in order that it produce a determinate effect, it must, of necessity, be determined to some certain one, which has the nature of an end. And just as this determination is effected, in the rational nature, by the "rational appetite," which is called the will; so, in other things, it is caused by their natural inclination, which is called the "natural appetite."

Nevertheless it must be observed that a thing tends to an end, by its action or movement, in two ways: first, as a thing, moving itself to the end, as man; secondly, as a thing moved by another to the end, as an arrow tends to a determinate end through being moved by the archer who directs his action to the end. Therefore those things that are possessed of reason, move themselves to an end; because they have dominion over their actions through their free-will, which is the "faculty of will and reason." But those things that lack reason tend to an end, by natural inclination, as being moved by another and not by themselves; since they do not know the nature of an end as such, and consequently cannot ordain anything to an end, but can be ordained to an end only by another. For the entire irrational nature is in comparison to God as an instrument to the principal agent, as stated above (1, Question 22, Article 2, ad 4; 1, Question 103, Article 1, ad 3). Consequently it is proper to the rational nature to tend to an end, as directing and leading itself to the end: whereas it is proper to the irrational nature to tend to an end, as directed or led by another, whether it apprehend the end, as do irrational animals, or do not apprehend it, as is the case of those things which are altogether void of knowledge.

Reply to Objection 1: When a man of himself acts for an end, he knows the end: but when he is directed or led by another, for instance, when he acts at another's command, or when he is moved under another's compulsion, it is not necessary that he should know the end. And it is thus with irrational creatures.

Reply to Objection 2: To ordain towards an end belongs to that which directs itself to an end: whereas to be ordained to an end belongs to that which is directed by another to an end. And this can belong to an irrational nature, but owing to some one possessed of reason.

Reply to Objection 3: The object of the will is the end and the good in universal. Consequently there can be no will in those things that lack reason and intellect, since they cannot apprehend the universal; but they have a natural appetite or a sensitive appetite, determinate to some particular good. Now it is clear that particular causes are moved by a universal cause: thus the governor of a city, who intends the common good, moves, by his command, all the particular departments of the city. Consequently all things that lack reason are, of necessity, moved to their particular ends by some rational will which extends to the universal good, namely by the Divine will.

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod agere propter finem sit proprium rationalis naturae. Homo enim, cuius est agere propter finem, nunquam agit propter finem ignotum. Sed multa sunt quae non cognoscunt finem, vel quia omnino carent cognitione, sicut creaturae insensibiles; vel quia non apprehendunt rationem finis, sicut bruta animalia. Videtur ergo proprium esse rationalis naturae agere propter finem.

Argumentum 2

Praeterea, agere propter finem est ordinare suam actionem ad finem. Sed hoc est rationis opus.

Ergo non convenit his quae ratione carent.

Argumentum 3

Praeterea, bonum et finis est obiectum voluntatis.

Sed voluntas in ratione est, ut dicitur in III de anima.

Ergo agere propter finem non est nisi rationalis naturae.

Sed Contra

Sed contra est quod philosophus probat in II physic., quod non solum intellectus, sed etiam natura agit propter finem.

Corpus

Respondeo dicendum quod omnia agentia necesse est agere propter finem. Causarum enim ad invicem ordinatarum, si prima subtrahatur, necesse est alias subtrahi. Prima autem inter omnes causas est causa finalis. Cuius ratio est, quia materia non consequitur formam nisi secundum quod movetur ab agente, nihil enim reducit se de potentia in actum. Agens autem non movet nisi ex intentione finis. Si enim agens non esset determinatum ad aliquem effectum, non magis ageret hoc quam illud, ad hoc ergo quod determinatum effectum producat, necesse est quod determinetur ad aliquid certum, quod habet rationem finis. Haec autem determinatio, sicut in rationali natura fit per rationalem appetitum, qui dicitur voluntas; ita in aliis fit per inclinationem naturalem, quae dicitur appetitus naturalis. Tamen considerandum est quod aliquid sua actione vel motu tendit ad finem dupliciter, uno modo, sicut seipsum ad finem movens, ut homo; alio modo, sicut ab alio motum ad finem, sicut sagitta tendit ad determinatum finem ex hoc quod movetur a sagittante, qui suam actionem dirigit in finem. Illa ergo quae rationem habent, seipsa movent ad finem, quia habent dominium suorum actuum per liberum arbitrium, quod est facultas voluntatis et rationis. Illa vero quae ratione carent, tendunt in finem per naturalem inclinationem, quasi ab alio mota, non autem a seipsis, cum non cognoscant rationem finis, et ideo nihil in finem ordinare possunt, sed solum in finem ab alio ordinantur. Nam tota irrationalis natura comparatur ad deum sicut instrumentum ad agens principale, ut supra habitum est.

Et ideo proprium est naturae rationalis ut tendat in finem quasi se agens vel ducens ad finem, naturae vero irrationalis, quasi ab alio acta vel ducta, sive in finem apprehensum, sicut bruta animalia, sive in finem non apprehensum, sicut ea quae omnino cognitione carent.

Ad 1

Ad primum ergo dicendum quod homo, quando per seipsum agit propter finem, cognoscit finem, sed quando ab alio agitur vel ducitur, puta cum agit ad imperium alterius, vel cum movetur altero impellente, non est necessarium quod cognoscat finem. Et ita est in creaturis irrationalibus.

Ad 2

Ad secundum dicendum quod ordinare in finem est eius quod seipsum agit in finem. Eius vero quod ab alio in finem agitur, est ordinari in finem. Quod potest esse irrationalis naturae, sed ab aliquo rationem habente.

Ad 3

Ad tertium dicendum quod obiectum voluntatis est finis et bonum in universali. Unde non potest esse voluntas in his quae carent ratione et intellectu, cum non possint apprehendere universale, sed est in eis appetitus naturalis vel sensitivus, determinatus ad aliquod bonum particulare. Manifestum autem est quod particulares causae moventur a causa universali, sicut rector civitatis, qui intendit bonum commune, movet suo imperio omnia particularia officia civitatis. Et ideo necesse est quod omnia quae carent ratione, moveantur in fines particulares ab aliqua voluntate rationali, quae se extendit in bonum universale, scilicet a voluntate divina.